GO:0102772 sphingolipid C4-monooxygenase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0102772 (sphingolipid C4-monooxygenase activity) catalyzes the 4-hydroxylation of dihydroceramide to phytoceramide, a reaction that requires Fe(II)-[cytochrome b5], H+, and O2.
• This activity is synonymous with sphingolipid long-chain base 4-hydroxylase activity and is a molecular_function in the GO ontology.
• The reaction consumes two Fe(II)-[cytochrome b5] equivalents and produces two Fe(III)-[cytochrome b5] equivalents plus water, linking sphingolipid synthesis to redox metabolism.
• Phytoceramide and its downstream sphingolipids influence membrane properties, stress responses, and aging-related pathways in muscle and other tissues.
• Sphingolipid metabolic remodeling, including hydroxylation steps, has been implicated in drug-induced hepatotoxicity and in anti-inflammatory signaling by Bacteroides sphingolipids.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable causal testing of C4-monooxygenase genes in sphingolipid biology and disease.
Description
Sphingolipid C4-monooxygenase activity (GO:0102772) is a molecular function that introduces a hydroxyl group at the C4 position of the sphingoid long-chain base, converting a dihydroceramide into a phytoceramide. This modification changes the biophysical properties of sphingolipids and influences membrane organization, signaling, and stress responses. The reaction is formally described as: a dihydroceramide + 2 Fe(II)-[cytochrome b5] + 2 H+ + O2 = a phytoceramide + 2 Fe(III)-[cytochrome b5] + H2O. Because the enzyme uses cytochrome b5 as an electron donor, the activity sits at the interface of sphingolipid metabolism and cellular redox chemistry. Researchers study GO:0102772 to understand how hydroxylated sphingolipids contribute to normal physiology and to diseases ranging from metabolic and inflammatory conditions to age-related muscle decline. The term is also relevant to drug safety, as disturbing cholesterol and sphingolipid metabolism can contribute to crizotinib hepatotoxicity. In this article, we summarize the definition, mechanism, key genes, regulation, disease links, and experimental models for GO:0102772, with an emphasis on CRISPR-based approaches for causal validation.
sphingolipid C4-monooxygenase activity At A Glance
| GO ID | GO:0102772 |
|---|---|
| GO term | sphingolipid C4-monooxygenase activity |
| Ontology | molecular_function |
| Synonym | sphingolipid long-chain base 4-hydroxylase activity |
| Major function | Catalyzes 4-hydroxylation of dihydroceramide to phytoceramide using Fe(II)-[cytochrome b5], H+, and O2 |
| Reaction | a dihydroceramide + 2 Fe(II)-[cytochrome b5] + 2 H+ + O2 = a phytoceramide + 2 Fe(III)-[cytochrome b5] + H2O |
| Cofactor/electron donor | Cytochrome b5 (Fe(II)-[cytochrome b5]) |
| Substrate | Dihydroceramide |
| Product | Phytoceramide |
| Related process | Sphingolipid metabolism and membrane lipid remodeling |
What Is GO:0102772?
GO:0102772, sphingolipid C4-monooxygenase activity, is defined as the catalysis of the reaction: a dihydroceramide + 2 Fe(II)-[cytochrome b5] + 2 H+ + O2 = a phytoceramide + 2 Fe(III)-[cytochrome b5] + H2O. In simpler terms, it is the enzyme activity that adds a hydroxyl group to the fourth carbon of the sphingoid base, using cytochrome b5 as the electron donor and molecular oxygen as the oxygen source. The synonym sphingolipid long-chain base 4-hydroxylase activity reflects this chemistry. This is a molecular_function term, meaning it describes what the protein does at the biochemical level rather than a whole pathway or cellular location.
Why Is sphingolipid C4-monooxygenase activity Important in Cell Biology?
GO:0102772 is important because the 4-hydroxylation of sphingoid bases alters the physical properties of sphingolipids and thereby affects membrane dynamics, protein sorting, and cell signaling. Hydroxylated sphingolipids are also linked to metabolic and inflammatory responses, including Bacteroides-derived sphingolipids that promote anti-inflammatory responses through the mevalonate pathway. In aging and muscle biology, sphingolipid accumulation has been associated with sarcopenia, and reducing sphingolipids can counteract age-related muscle decline. Sphingolipid and methionine metabolism are also interconnected in aging. Additionally, perturbations in cholesterol and sphingolipid metabolism can contribute to drug-induced hepatotoxicity, highlighting the clinical relevance of this activity. Because the reaction depends on cytochrome b5 and oxygen, it connects sphingolipid biosynthesis to redox and oxygen-sensing biology.
• Defines a specific enzymatic step that generates phytoceramide, a hydroxylated sphingolipid with distinct biophysical properties.
• Links sphingolipid metabolism to cytochrome b5-dependent redox chemistry and oxygen consumption.
• Contributes to membrane lipid remodeling and sphingolipid transport processes.
• Has been associated with age-related muscle decline, where sphingolipid accumulation contributes to sarcopenia.
• Connects to aging through sphingolipid and methionine metabolism.
• Relevant to inflammatory signaling, as Bacteroides sphingolipids promote anti-inflammatory responses via the mevalonate pathway.
• Implicated in drug-induced hepatotoxicity when cholesterol and sphingolipid metabolism are disturbed.
• Provides a target for CRISPR-based causal studies of sphingolipid genes in metabolic and aging research.
• Supports research on hematopoietic stem cell self-renewal through sphingolipid modulation.
• Offers a biochemical handle for developing assays and models of sphingolipid hydroxylation.
Molecular Mechanism of sphingolipid C4-monooxygenase activity
Substrate recognition and binding
In simple terms: The enzyme first grabs a dihydroceramide molecule and positions it for modification.
The reaction begins with binding of a dihydroceramide, the substrate that will be hydroxylated at the C4 position of the sphingoid base. The enzyme must recognize the long-chain base and present it to the catalytic site in a geometry that allows oxygen insertion. This step determines specificity for dihydroceramide over other sphingolipids.
Electron transfer from cytochrome b5
In simple terms: The enzyme receives electrons from cytochrome b5 to activate oxygen.
The reaction requires two Fe(II)-[cytochrome b5] equivalents, which serve as electron donors. These electrons reduce the active-site iron and help activate molecular oxygen for the hydroxylation reaction. After electron transfer, the cytochrome b5 is oxidized to Fe(III)-[cytochrome b5].
Oxygen activation and C4 hydroxylation
In simple terms: Oxygen is split and one oxygen atom is added to the sphingolipid.
Molecular oxygen (O2) is consumed during the reaction, and one oxygen atom is incorporated into the phytoceramide product. The other oxygen atom is reduced to water. This monooxygenase chemistry is typical of cytochrome b5-dependent fatty acid and sphingolipid hydroxylases.
Product formation and release
In simple terms: The modified sphingolipid, phytoceramide, is released.
The reaction yields a phytoceramide, which contains a hydroxyl group at C4 of the sphingoid base. The products also include two Fe(III)-[cytochrome b5] equivalents and H2O. The phytoceramide can then be further metabolized into complex sphingolipids or participate in signaling and membrane structure.
Cofactors and redox balance
In simple terms: The reaction depends on iron and cytochrome b5, linking it to cellular redox state.
The catalytic cycle requires Fe(II)-[cytochrome b5] as an electron donor and generates Fe(III)-[cytochrome b5]. This means the activity is sensitive to the availability and redox state of cytochrome b5 and iron. Consequently, cellular redox balance and oxygen availability can influence the rate of phytoceramide production.
Key Genes Involved in GO:0102772 sphingolipid C4-monooxygenase activity
The following genes and proteins are directly or indirectly associated with sphingolipid C4-monooxygenase activity, its substrates, cofactors, or downstream sphingolipid metabolism, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SUR2 | Sphingolipid long-chain base 4-hydroxylase in yeast | Model for C4-hydroxylation and phytoceramide synthesis |
| SUR2 homologs | Putative sphingolipid C4-monooxygenase in other organisms | Comparative studies of hydroxylation and stress responses |
| CYB5A | Cytochrome b5, electron donor for the reaction | Redox partner for C4-monooxygenase activity |
| CYB5B | Cytochrome b5 family member | Potential electron donor in sphingolipid hydroxylation |
| DEGS1 | Dihydroceramide desaturase, upstream of dihydroceramide | Controls substrate availability for C4-hydroxylation |
| DEGS2 | Dihydroceramide desaturase-like enzyme | May influence dihydroceramide pools |
| CERS1 | Ceramide synthase, produces dihydroceramide | Upstream of C4-monooxygenase substrate |
| CERS2 | Ceramide synthase, produces dihydroceramide | Upstream of C4-monooxygenase substrate |
| CERS4 | Ceramide synthase, produces dihydroceramide | Upstream of C4-monooxygenase substrate |
| SPTLC1 | Serine palmitoyltransferase subunit, first step of sphingolipid synthesis | Controls flux into sphingolipid pathway |
| SPTLC2 | Serine palmitoyltransferase subunit | Controls flux into sphingolipid pathway |
| ORMDL1 | Negative regulator of serine palmitoyltransferase | Regulates sphingolipid synthesis and metabolic health |
| ORMDL2 | Negative regulator of serine palmitoyltransferase | Regulates sphingolipid synthesis |
| ORMDL3 | Negative regulator of serine palmitoyltransferase | Linked to inflammatory and metabolic phenotypes |
| SPHK1 | Sphingosine kinase 1, produces S1P | Downstream sphingolipid signaling in muscle and exercise |
| S1PR1 | Sphingosine-1-phosphate receptor 1 | Mediates S1P signaling in slow-twitch myofibers |
| S1PR2 | Sphingosine-1-phosphate receptor 2 | Mediates S1P signaling in muscle adaptation |
How Is sphingolipid C4-monooxygenase activity Regulated?
Sphingolipid C4-monooxygenase activity is regulated at multiple levels. Substrate availability is controlled by upstream enzymes such as serine palmitoyltransferase and ceramide synthases, which determine the pool of dihydroceramide. The ORMDL proteins negatively regulate serine palmitoyltransferase and thereby influence flux into the sphingolipid pathway, indirectly affecting C4-hydroxylation. Redox state and cytochrome b5 availability also regulate the reaction because the enzyme requires Fe(II)-[cytochrome b5] as an electron donor. In aging and metabolic contexts, sphingolipid metabolism is coordinated with methionine metabolism, suggesting broader metabolic regulation. Additionally, sphingolipid transport and membrane organization can affect access of the enzyme to its substrate. Sphingosine-1-phosphate signaling downstream of sphingolipid metabolism is regulated by SPHK1 and S1PR1/S1PR2 in muscle adaptation, providing a physiological context for regulation.
sphingolipid C4-monooxygenase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SUR2 | Sphingolipid hydroxylation and stress response | Yeast knockout and point-mutation models |
| CYB5A | Redox metabolism and drug-induced hepatotoxicity | Hepatocyte knockout and overexpression |
| ORMDL3 | Inflammatory and metabolic phenotypes | Knockout and knock-in in immune cells |
| SPHK1 | Muscle adaptation and sarcopenia | Skeletal muscle knockout and overexpression |
| S1PR1 | Sphingosine-1-phosphate signaling in muscle | Knockout and point-mutation models |
Sphingolipid C4-monooxygenase activity and drug-induced hepatotoxicity
Disturbing cholesterol and sphingolipid metabolism can contribute to crizotinib hepatotoxicity, and squalene epoxidase inhibition alters these pathways. This suggests that perturbations in sphingolipid hydroxylation and related metabolic steps may influence drug-induced liver injury. Researchers can use hepatocyte models to test whether C4-monooxygenase activity modulates sensitivity to crizotinib.
Sphingolipid C4-monooxygenase activity in aging and sarcopenia
Sphingolipids accumulate in aged muscle, and their reduction counteracts sarcopenia. Sphingolipid and methionine metabolism are also linked in aging. These findings imply that enzymes controlling sphingolipid hydroxylation, including C4-monooxygenase activity, may contribute to age-related muscle decline. Experimental models of muscle aging can be used to test this hypothesis.
Sphingolipid C4-monooxygenase activity and inflammation
Bacteroides sphingolipids promote anti-inflammatory responses through the mevalonate pathway. Because C4-hydroxylation modifies sphingolipid structure, it may influence the immunomodulatory properties of sphingolipids. This creates opportunities to study host-microbe interactions and inflammatory signaling in relevant cell models.
Sphingolipid C4-monooxygenase activity and hematopoietic stem cell biology
Sphingolipid modulation activates proteostasis programs that govern human hematopoietic stem cell self-renewal. Hydroxylated sphingolipids may participate in these programs, although direct evidence for C4-monooxygenase activity in this context requires further study. Hematopoietic stem cell models can be used to dissect these mechanisms.
From sphingolipid C4-monooxygenase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of C4-monooxygenase activity alter phytoceramide levels? | CRISPR knockout of candidate hydroxylase genes |
| Does a specific catalytic residue mediate C4-hydroxylation? | Point-mutation knock-in of catalytic residues |
| Can tagged C4-monooxygenase be used to study localization? | Tagged knock-in with fluorescent or affinity tags |
| Does overexpression of C4-monooxygenase change sphingolipid profiles? | Overexpression cell models |
| Does C4-monooxygenase activity modulate drug-induced hepatotoxicity? | Hepatocyte knockout and overexpression |
| Does C4-monooxygenase activity affect muscle aging phenotypes? | Muscle cell knockout and overexpression |
How to Study the sphingolipid C4-monooxygenase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Lipidomics (LC-MS) | Dihydroceramide and phytoceramide levels | Quantifying C4-monooxygenase activity in cells |
| In vitro enzyme assay | Catalytic activity and cofactor dependence | Testing point mutants and inhibitors |
| CRISPR knockout screen | Genes affecting sphingolipid hydroxylation | Discovery of regulators |
| RNA-seq | Transcriptional changes in sphingolipid genes | Aging and metabolic studies |
| Proteomics | Protein abundance and modifications | Pathway analysis after perturbation |
| Fluorescence imaging | Localization of tagged C4-monooxygenase | Subcellular distribution studies |
| Metabolic flux analysis | Flux through sphingolipid pathway | Isotope tracing |
| Co-immunoprecipitation | Protein-protein interactions with cytochrome b5 | Redox partner identification |
Lipidomics and mass spectrometry
Mass spectrometry-based lipidomics can quantify dihydroceramide and phytoceramide levels to assess C4-monooxygenase activity. This approach is essential for measuring substrate consumption and product formation in cells and tissues. It can be combined with stable isotope labeling to trace flux through the sphingolipid pathway.
Enzymatic assays with cytochrome b5
In vitro assays can reconstitute the reaction using dihydroceramide, cytochrome b5, and appropriate redox partners. These assays measure oxygen consumption or product formation to determine catalytic activity. They are useful for testing point mutations that affect electron transfer or substrate binding.
CRISPR-based genetic screens
CRISPR knockout screens can identify genes that regulate sphingolipid hydroxylation and phytoceramide production. Such screens can be coupled with lipidomics or reporter readouts to discover modifiers of C4-monooxygenase activity. This approach is powerful for uncovering pathways that impinge on sphingolipid metabolism.
Transcriptomics and proteomics
RNA-seq and proteomics can reveal changes in sphingolipid pathway gene expression upon perturbation of C4-monooxygenase activity. These methods help place the enzyme in the broader context of aging and metabolic regulation. They can also identify compensatory changes in related pathways.
How CRISPR Can Be Used to Study GO:0102772 sphingolipid C4-monooxygenase activity
Knockout
CRISPR knockout of candidate C4-monooxygenase genes can abolish phytoceramide production and reveal loss-of-function phenotypes. Knockout models are useful for testing whether the enzyme is required for specific sphingolipid-dependent processes. They can be combined with lipidomics to confirm substrate accumulation.
Point Mutation
Point mutations can be introduced into catalytic residues or cytochrome b5-binding sites to dissect the mechanism of C4-hydroxylation. Such models help distinguish between defects in substrate binding, electron transfer, and oxygen activation. They are valuable for structure-function studies.
Knock-in
Knock-in of tagged versions of the enzyme allows visualization and affinity purification of the protein. This approach can reveal subcellular localization and interaction partners. It is also useful for studying dynamic regulation of the enzyme.
Overexpression
Overexpression of C4-monooxygenase can increase phytoceramide levels and test gain-of-function phenotypes. This is useful for determining whether increased hydroxylation is sufficient to alter membrane properties or signaling. Overexpression models can also be used in drug toxicity studies.
How EDITGENE Supports sphingolipid C4-monooxygenase activity Research
Researchers studying sphingolipid C4-monooxygenase activity-related genes often need to determine whether a candidate gene is causally involved in phytoceramide production, membrane remodeling, or disease phenotypes. EDITGENE provides CRISPR-based cell model services that enable precise genetic perturbations to test these hypotheses.
Contact EDITGENE today to design your custom CRISPR model for sphingolipid C4-monooxygenase activity research.
Frequently Asked Questions About sphingolipid C4-monooxygenase activity
What is sphingolipid C4-monooxygenase activity?
It is the enzyme activity that converts dihydroceramide to phytoceramide by adding a hydroxyl group at C4, using cytochrome b5 and oxygen.
What is the GO ID for sphingolipid C4-monooxygenase activity?
The GO ID is GO:0102772.
What reaction does GO:0102772 catalyze?
It catalyzes: a dihydroceramide + 2 Fe(II)-[cytochrome b5] + 2 H+ + O2 = a phytoceramide + 2 Fe(III)-[cytochrome b5] + H2O.
What genes are involved in sphingolipid C4-monooxygenase activity?
Genes include SUR2 and its homologs, CYB5A, CYB5B, and upstream sphingolipid genes such as DEGS1, CERS1-4, and SPTLC1/2.
What is the synonym for GO:0102772?
The synonym is sphingolipid long-chain base 4-hydroxylase activity.
How is sphingolipid C4-monooxygenase activity regulated?
It is regulated by substrate availability, ORMDL-mediated control of serine palmitoyltransferase, and redox state of cytochrome b5.
What diseases are linked to sphingolipid C4-monooxygenase activity?
It has been associated with drug-induced hepatotoxicity, aging and sarcopenia, inflammation, and hematopoietic stem cell biology.
How can I study sphingolipid C4-monooxygenase activity?
You can use lipidomics, in vitro enzyme assays, CRISPR screens, and transcriptomics/proteomics.
What model systems are used for GO:0102772 research?
Yeast, hepatocytes, muscle cells, immune cells, and hematopoietic stem cells are used.
Why is sphingolipid C4-monooxygenase activity important for aging?
Sphingolipids accumulate in aged muscle, and their reduction counteracts sarcopenia, suggesting a role for hydroxylation in aging.
Conclusion
GO:0102772, sphingolipid C4-monooxygenase activity, is a cytochrome b5-dependent monooxygenase reaction that generates phytoceramide and influences membrane properties, signaling, and stress responses. Its connections to aging, inflammation, drug toxicity, and stem cell biology make it a compelling target for mechanistic and translational research. CRISPR-based knockout, point-mutation, knock-in, and overexpression models provide powerful tools to test causal roles of this activity in health and disease. By combining lipidomics, enzymology, and genetic screens, researchers can dissect how C4-hydroxylation shapes sphingolipid biology.
References
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- 6. Leng M et al.. 2025. Mitophagy-mediated S1P facilitates muscle adaptive responses to endurance exercise through SPHK1-S1PR1/S1PR2 in slow-twitch myofibers.. Autophagy 21(10):2111-2129 PMID: 40181214
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